1. Field of the Invention
The present invention relates generally to barriers for preventing vehicle passage and more particularly to a survivable anti-terrorist vehicle crash barrier incorporating replaceable impact energy absorbing components pursuant to Contract No. DE-AC04-76DP00789 awarded by the U.S. Department of Energy.
2. Description of the Prior Art
Terrorist threats especially to governmental facilities, such as embassies and military compounds, have become more acute in recent years. To prevent terrorists and other adversaries from using ground vehicles to penetrate the perimeters of such restricted and protected areas, the design and installation of an entrance barrier selectively actuatable to prevent passage of unauthorized vehicles and to permit passage of authorized vehicles is greatly needed, in addition to fixed barriers around the perimeter of the compound.
Many different vehicle barriers appear in the prior patent art for achievement of various goals, such as improving vehicular highway safety, impact energy absorption and traffic direction control. Representative examples are the prior art barriers disclosed in U.S. Pat. Nos. to Gravisse (3,448,963), Peterson et al (3,712,589), Brubaker (4,007,917), Meinzer (4,101,115), Hurst, Jr. (4,332,503), Gertz et al (4,352,484), Tyers (4,367,975), Meinzer (4,407,484) and Dickinson (4,490,068). However, none of these prior art barriers appear suitable for defending against vehicular crash-type penetrations through gates, entrances and other portals to governmental facilities.
Of all the above-cited patents, the Dickinson patent discloses a barrier that appears to have promise in effectively controlling normal vehicular traffic at entrances and exits of facilities such as parking lots and the like. Specifically, the barrier of the Dickinson patent is a below-pavement pivotally-mounted structure having an elongated curb-like configuration. Via operation of a pair of hydraulic cylinders, the curb-like barrier of Dickinson is selectively actuatable between a retracted position in which the barrier is disposed below pavement level with its outer surface member flush with the pavement to permit desired traffic flow over it and a raised position in which the barrier projects above pavement level giving the appearance of a curb-like structure to prevent traffic flow over it.
One major drawback of the barrier of Dickinson is that it presents an essentially rigid structure to the incoming vehicle. No substantial portion of the impacting vehicle's kinetic energy can be absorbed by the barrier without causing significant structural damage to it. Another important drawback is that the hydraulic cylinders of the barrier which pivot and position the curb-like structure are attached to it so that they are likely to be damaged along with it.
It appears that no amount of "beefing up" of the structural makeup of the Dickinson barrier would overcome the above-mentioned drawbacks. Although the Dickinson barrier may successfully stop an incoming vehicle, the barrier would undoubtedly be damaged so extensively as to not survive the impact. Complete replacement of the barrier would be necessary. Rather than stopping the vehicle, it is more likely that the abruptness of the vehicle's impact with the rigid barrier of Dickinson would propel a significant portion of the vehicle and its payload a distance beyond the barrier sufficient to accomplish at least part of the terrorist's objective.
In view of the above-noted drawbacks in the barrier of the Dickinson patent which also apply generally to most commercially available vehicle barriers, it is apparent that a pressing need remains unfulfilled for an anti-terrorist vehicle crash barrier that will be effective in stopping the entire vehicle, is survivable and can be placed back into operative condition within a short period of time.